I'm using Fedora Core 1, with SendMail 8.12.10.
The relay is closed, except for the company's internal network, which is 10.0.0.0/24.
But there's one flaw: if I connect to the Internet from home, and I send a message using the company's sendmail as relay, from email@example.com
, the server accepts it.
So my users are receiving loads of spam from spammers who identify themselves as firstname.lastname@example.org
, and worse, using our own server as relay.
I thought that this would only happen if I configured sendmail with:
but this is not the case.
Does anyone know how to solve this?